DE69402744T2 - Tube for storing and dispensing a water-containing and possibly flavored or perfumed product - Google Patents

Abstract

The subject of the invention is a storage and dispensing (distribution) tube (C) for a product, for example a water-containing product which may be flavoured or perfumed, comprising a dispensing head which is fixed onto a flexible multilayer skirt, this skirt essentially containing an intermediate polymer layer (20) which has a barrier effect with respect to oxygen and flavours or perfumes, the said layer being sensitive to humidity, as well as, on each face of this intermediate layer, one or more polymer layers (1; 12,14,10) based on polyolefins, all of the said layers being bonded together in a continuous manner, characterised in that the set of layers situated on the inner face of the said intermediate layer having a barrier effect (1,21) has a total thickness of between 40 and 150 micrometres, so as better to conserve the flavour or the perfume which is or may be contained therein. This tube preferably includes one or two means which render the dispensing of the contained product easier and more complete. It applies to the industries for packaging products which are, for example, liquid, creamy or pasty. <IMAGE>

Description

The invention relates to a tube for storing and dispensing a generally liquid, cream or paste-like product, whereby the aroma or perfume contained in the product is well preserved by means of this tube.

From EP-A-0 084 922 = US-A-4 626 456 a tube is known for storing and dispensing a product which is, for example, flavored or perfumed and contains water, said tube comprising a dispensing head which is attached to a multilayer, flexible casing, said casing necessarily comprising an intermediate layer with a barrier effect for oxygen and flavors or fragrances which is sensitive to moisture, as well as one or more polymer layers based on polyolefin on each side of the intermediate layer, and all of these layers being connected to one another. The product contained is, for example, toothpaste and the intermediate layer with a barrier effect is, for example, made of EVA (ethylene-vinyl alcohol copolymer). The structure of the casing, without a metallic intermediate layer and with layers essentially made of polypropylene with an addition of powder of calcium carbonate, mica or talc, allows good stability of the compression folds of the tube.

Two disadvantages have been observed with such a tube. Firstly, as is known from US-A-4 407 897, EVA is very sensitive to moisture. Toothpaste usually contains 20 to 30 percent moisture by mass, and in multi-layer tubes with a barrier layer made of EVA, a significant loss of aroma has been observed in such a paste. Furthermore, it has been found that the stability of the compressed areas makes emptying the tube difficult.

Furthermore, from patent application GB-A-2 048 209 a tube for a product such as toothpaste with a casing made of a multi-layer plastic material is known, which has a suitable Deformability for repeated pressing and with increased resistance to delamination. This casing comprises at least an oxygen barrier layer made of EVA or PA (polyamide), an olefin layer and an adhesive layer made of modified olefin inserted between the two previous layers. The delamination of these layers is prevented by an elastic limit of the adhesive layer which is lower than that of the barrier layer and higher than that of the olefin layer. At the same time, the thickness of the olefin layer is greater than the sum of the thicknesses of the barrier layer and the adhesive layer and the product of the elastic limit and the thickness of the olefin layer is between 7 and 170 kg/cm; these means improve the deformability and recovery after each pressing of the tube. This document does not indicate how to avoid the losses of flavour which occur in the absence of delamination of the tube casing.

The applicant has attempted to develop a tube that better preserves the aroma or fragrance of a product contained therein. In addition, it has sought to ensure that this tube enables the product to be dispensed more easily and completely.

The subject of the invention is a tube as known from the first cited document, characterized in that the totality of the layers arranged on the inside of the intermediate layer with a barrier effect has a total thickness of between 55 and 140 µm, so that the aroma or fragrance of a product contained in the tube or which may subsequently be contained therein is better preserved.

The applicant's interpretation of this subject-matter is as follows: if the thickness of the layers arranged on the inside of the barrier layer is less than 55 µm, the moisture of the product passing through these layers quickly impairs the barrier properties of the barrier layer for oxygen and aromas and fragrances, and the Flavors or fragrances of the product can penetrate beyond this layer and even escape from the tube.

If the thickness of the layers in question is greater than 140 µm, the moisture does not reach the barrier layer in sufficient quantity to affect its properties, but the aromas or fragrances are absorbed and stored in significant quantities by these layers. These aromas or fragrances are typically compounds dissolved in the water contained in the product, and their evaporation and absorption follow, to a first approximation, the evaporation and absorption of the water, which represents the moisture of the product.

Despite the importance of these effects, the document GB-A-2 048 209 does not allow them to be foreseen and there is no direct or indirect reference to the thickness of the layers arranged on the inside of the barrier layer.

Even better results in preserving the aromas or fragrances of the product contained in the tube are obtained when the total thickness of the layers arranged on the intermediate barrier layer is between 65 and 130 µm, with an optimum of 70 to 120 µm.

The above conditions allow the use of inexpensive polyolefins, namely the polyethylene family, for the structure of the sheath, and provide excellent welding of the layers to one another. The user was therefore interested in a tube in which the polyolefin-based polymer layers of the sheath consist, on the one hand, of an internal surface layer of low or very low density polyethylene or linear low density polyethylene with a specific weight of between 0.86 and 0.93 g/cm3 and, on the other hand, of other layers each made of low density polyethylene (PE-LD) with a specific weight between 0.90 and 0.93 g/cm³ or made of high density polyethylene (PE-HD) with a specific gravity between 0.935 and 0.97 g/cm³.

In an effort to simplify and more completely dispense the product stored in the tube according to the invention, which better preserves the aroma or perfume of the product, the applicant has found that local dents caused by squeezing the tube can be avoided by improving the elastic resistance of the tube to compression. To this end, the polyethylene layers of the tube casing contain one or more layers of HDPE with a total thickness of 90 µm or more. Tests show that when the total thickness of the HDPE goes from 84 to 125 µm, the elastic resistance of the casing to compression more than doubles. When the thickness of the casing is between 260 and 380 µm, as in the case of the tube, the elastic resistance of the casing to compression is more than doubled. B. in the case of a toothpaste tube, this total thickness of the PE-HD layers is preferably between 100 and 140 µm, the surface layers preferably being made of PE-LD or, in the case of the inner layer, of linear low-density PE. For these surface layers, good ductility is desired, combined with, on the outside of the tube, good suitability for pressing in and, on the inside of the tube, good resistance to the formation of microcracks. The above-mentioned ranges of the total thickness of the PE-HD are to be changed relative to the thickness of the jacket if this is outside the stated range. In this increase in the elastic counterforce of the jacket against compression, the influence of the intermediate layer with a barrier effect can be taken into account, which has higher characteristics than the PE-HD of the same thickness. In the 0. g. The jacket thickness is the sum of the doubled thickness of the barrier layer and the total thickness of the PE-HD layers, preferably between 130 and 180 µm, regardless of whether the previous condition relating to the total thickness of the PE-HD layers alone is met or not.

In order to facilitate production and thereby obtain surface layers of the type described above, i.e. typically made of PE-LD, to achieve the desired PE-HD total thickness, it is preferable to use:

- a first PE-HD layer interposed between the internal surface layer and a first intermediate layer of PE-LD, which in turn is arranged within the intermediate layer with barrier effect; or

- a second layer of PE-HD inserted between an external layer of PE-LD and a second intermediate layer of PE-LD, which in turn is arranged outside the intermediate layer with barrier effect.

Such first and second layers of PE-HD can be conveniently used simultaneously, with their thicknesses being between 10 and 50 µm and between 60 and 140 µm, respectively.

These PE-HD layer(s) are typically "melt-continuous" bonded to the layers between which they are inserted, their materials being fusible and the manufacturing process having resulted in a weld with perfect structural continuity between the layers. A PE-HD layer inserted in this way can be recognized in cross-section by micro-hardness measurements, but not by the appearance of the structure. Layers welded in this way are obtained by co-extruding the shell or by welding a multi-layer blank with overlapping edges, which in turn has been obtained after assembly by one or more common rolling passes using a coating produced by extruding molten PE.

Typically, the first and second PE interlayers are each bonded to one side of the barrier interlayer they surround by a tie layer, often made of EAA or EMA. These five layers are often used in the form of a prepared multilayer film in which the moisture-sensitive barrier layer is relatively well protected in this respect.

Moisture-sensitive materials for the barrier intermediate layer of the jacket include: EVAs and PVAs (polyvinyl alcohols), whose degradation by moisture is described in the previously cited US-A-407 897, and, with a lower degree of sensitivity, polyamides and modified polyamides, e.g. polymetaxylylene adipamide (MXD6). Such a barrier intermediate layer in the jacket typically has a thickness of between 0.01 and 0.05 µm, and several barrier layers can be present, which together preferably have the above-mentioned thickness.

In order to make the dispensing of the product stored in the tube according to the invention easier and more complete, the Applicant has developed a second means, which can be used alone or in combination with the first means, which requires a minimum thickness of the PE-HD layers of the sheath of more than 90 µm.

This second means consists in providing a compressible annular shoulder between the skirt and the neck of the tube. As is known, the shoulders of known tubes are rigid due to the way they are manufactured and form a kind of wall which retains part of the product to be dispensed, typically a cream or paste. The manufacturing process which is the subject of French patent application No. 93 01065 of 27 January 1993 filed by the applicant preferably results in a tube in which the dispensing head comprises a neck of smaller diameter than the skirt and an annular shoulder connecting the neck to the skirt, this shoulder being smooth and having a thickness of between 0.9 and 1.35 times, preferably between 0.8 and 1.25 times, the thickness of the tube, in structural continuity with the skirt. and has flattened folds welded together, said shoulder being slightly laterally compressible. This shoulder and typically at least part of the neck of the tube contain the barrier layer(s) of the tube casing in the form of folded and flattened extensions contained in the aforementioned flattened and welded folds, which in turn are extensions of the barrier layer(s) of the casing. The neck may be completed by an annular collar made of PE welded to the head, said shoulder remaining at least half compressible.

The second means thus simultaneously provides the possibility of an easier and more complete release of the product contained in the tube and an improved protection of its aroma or fragrance at the level of the tube head. The locally thinned folds of a barrier layer of the shoulders usually together satisfy the preferred condition of a total thickness of 0.01 to 0.05 mm with improved efficiency. The manufacturing process leading to this second means is briefly described in the examples.

Advantage of the invention

- It provides a means of preserving the aroma or fragrance of the product contained in it in a cost-effective coating structure;

- Furthermore, according to its preferred characteristics, it allows to limit local dents in the tube when pressed, this acts on a larger area of the tube and becomes lighter each time;

- Alternatively, or in conjunction with the effect of limiting the indentation of the casing, it provides the possibility of compressing the head laterally and thus expelling the product more easily and completely at the end of the dispensing process.

Examples

Figures 1 to 3 show a section of the casings of three tubes, the first (Figure 1, comparison tube) not according to the invention, the other two (Figures 2 and 3) according to the invention

Figure 4 shows, in axial section, an arrangement for measuring the elastic resistance of a tube casing to compression, associated with the first means, which provides for an easier and more complete dispensing of the product.

Figure 5 is a graphical representation of the weight gain of jacket samples as a function of the total thickness of the layers within the barrier layer in an aroma loss test.

Figure 6 graphically shows the change in the resistance of the tube casing to compression as a function of the total thickness of the PE-HD layers present therein.

Figures 7 to 10 relate to the second means leading to improved delivery, a compressible shoulder. Figure 7 shows in cavalier perspective a comparative tube obtained by molding at ambient temperature.

Figure 8 shows a tube according to the invention with a compressible shoulder in an axial half-section.

Figure 9 shows another tube with a compressible shoulder, provided with an annular collar made of PE forming the outside of its neck, in axial half-section.

Figure 10 shows a microscopic representation of the upper part of the shoulder of this tube and the connection of this shoulder with the annular crown in axial section.

1) Structure of the shells of the tubes from Figures 1 to

All three of these structures comprise an intermediate barrier layer 20 made of EVA with a thickness of 0.02 mm, which is bonded to PE layers via two adhesive layers 21 and 22 made of EMA copolymer (ethylene-methacrylic acid copolymer), each with a thickness of 0.01 mm, which, in contact with these bonding layers 21 and 22, comprise PE-LD with a specific weight of 0.92 g/cm³ as layer 1 or as sub-intermediate layer 11 or 12. The boundaries between layers of different types are indicated by solid lines, whereas the invisible boundaries between PE-LD and PE-HD sub-layers, which result from their assembly in at least a superficially molten state, are shown in dashed lines.

The term "sublayer" is used here for those layers of which at least one boundary surface is invisible, but which are full-fledged layers in terms of the technical functions considered in the present invention. They can be determined by microhardness measurements.

It can also be seen in Figures 1 to 3 that the sublayers of PE-HD 13 and 14 with a specific weight of 0.95 g/cm³ are each located between a said intermediate sublayer of PE-LD 11 or 12 and an internal sublayer of linear low density PE or an external sublayer of PE-LD.

From the inside of the mantle outwards, the successive thicknesses are as follows, with details of the sublayers given between parentheses:

- Tube A (Figure 1): PE-LD layer "1" 0.035 mm; EMA layer "21" 0.01 mm, EVA layer "20" 0.02 mm, EMA layer "22" 0.01 mm; PE layers "12 + 14 + 10" 0.215 mm (PE-LD "12" 0.082 mm - PE-HD "14" 0.0105 mm - outer PE-LD "10" 0.032 mm)

- Tube B (Figure 2): Inner PE layer "100 + 13 + 11" 0.09 mm (inner linear low density PE "100" 0.01 mm - PE-HD "13" 0.02 mm - PE-LD "11" 0.06 mm); sequence EMA, EVA, EMA as in A; PE layer "12 + 14 + 10" 0.0215 mm with the same structure as in A.

- Tube C (Figure 3): Inner layer "1" made of PE-LD 0.0125 mm; Sequence EMA, EVA, EMA at A and B; PE layers "12 + 14 + 10" 0.175 mm (PE-LD "12" 0.073 mm - PE-HD "14" 0.084 mm - outer PE-LD "10" 0.018 mm.

The casings of tubes A, B, C were welded from raw foils with the above-mentioned structures and densities, then the tube heads were molded onto these casings.

2) Aroma loss tests

Circular cutouts of 50 mm diameter of the three qualities mentioned above, shown in Figures 1 to 3, were impregnated on the inner side of their shell, the side of layer 1 or 100, with an ordinary toothpaste containing 25% water and menthol in a container at 38 ºC for four weeks.

At the end of the test, the sample is cleaned of the toothpaste remaining on the surface. Its weight gain is determined, which provides information on the loss of water and aroma. The aim is to obtain a quality that, in this test, gives a weight gain per unit surface area of less than 1.2 mg/cm³ and preferably less than 0.66 mg/cm³. A meets the first criterion, but not the second. The results of the tests are shown in Table 1 and Figure 5.

The interpretation is as follows: There are no samples where the EVA barrier layer is exposed on the inside of the jacket, since such an EVA layer would be completely degraded by moisture during the manufacture of the corresponding multilayer film. For such a sample, one would theoretically observe a high weight increase in Figure 5, due to the ease with which moisture penetrates the EVA and settles in the areas outside the EVA. layers. At a layer thickness of 0.02 mm within the EVA, a significant increase in weight of over 2.5 mg/cm³ is still observed. The increase in weight decreases sharply when the thickness of the layers within the EVA exceeds 0.3 mm, and the steep linear section of the curve in which A lies corresponds to absorption with degradation of the EVA by the moisture and subsequent passage of the water and aroma through the EVA, which are then absorbed both by the layers outside the EVA 21, 12, 14 and 10 and by the inner layers such as 21 and 1. The decrease from A to B corresponds to a predominant effect of the protection of the EVA layer 20 due to the increasing thickness of the inner layers, and the increase again from B to C corresponds to the predominant influence of the absorption of water and aroma by the inner layers, whose thickness and thus also their absorption capacity increases, whereas the EVA is sufficiently protected.

3) Press test or indentation resistance test of the casing

A shell sample 15 is held so as to form a reproducible semicircular cylindrical dome 16 of 25 mm diameter and 100 mm length, which is pressed with a rigid rod 17 of 3 mm diameter along the straight line 18 which forms the apex of the dome. The dashed contour 19 shows the shape that the dome 16 assumes when the pressing in of the rod 17 has progressed at a constant speed.

A system (not shown) measures the counterforce exerted by the dome 16 or 19 on the rod 17 and determines its maximum. If this counterforce is strong, the corresponding tube casing resists the pressure better and its indentation remains at least partially in the elastic range, thus making it possible to avoid local constrictions, contrary to the teaching of document EP-A-0 084 922.

The results of these tests are shown in Table 2 and Figure 6. Points A, B, C lie on a line in Figure 6. In the absence of PE-HD in the sheath, which then consists entirely of PE-HD with the exception of the EVA and the thin adhesive layers 21 and 22 surrounding it, the counterforce is inevitably slightly positive (point Z). An increasing thickness of the PE-HD causes an increase in the counterforce of the sheath against compression, which accelerates between 40 and 70 µm (solid section of the curve ZX).

The effect is confirmed at the thickness of 90 µm, which is considered to be the minimum. Tube B according to the invention has a casing that resists compression well, while tube C is inadequate in this respect. Tube A, which is inadequate in terms of aroma loss and therefore lies outside the invention claimed in this application, has adequate compression resistance.

4) Second means for easier and more complete dispensing of the contained product: tube with compressible shoulder (Figures 7 to 10)

The method for manufacturing this tube consists in starting from a tubular blank longer than the jacket and in tapering a section of it by shaping this section while it is heated above the melting temperature of its surface layers - in the case of surface layers made of polyethylene, preferably between 140 and 220 ºC - and then compressing this section between tools so that it folds, these folds being perfectly welded together on each side and the surfaces of the shoulder typically being completely smooth.

Figure 7 shows a tube with an ambient formed shoulder, showing that the double folds such as 31 and 32 are inward or outwardly directed shafts 31 and 32, respectively, which have been compressed.

During the above-mentioned hot forming, the folds are strongly compressed, including those of the barrier layer 20 enclosed therein. A shoulder 33 that is thinner than the casing can be obtained. Figure 8 shows a tube according to the invention with a threaded neck, obtained directly by this hot forming, the inner tool and the annular slide of the outer tool forming the thread 35 of the neck between them at the end of the closed state. Figure 9 shows a tube 36 of the same type, obtained by hot forming, and then fitted with an annular outer collar 37 made of PE, which completes the neck of the tube. This ring 37 is perfectly welded to the outside and the top of the hot-formed tube 36, it has been applied by deformation under pressure of a PE annular blank heated to 160 ºC, thus forming in a pasty state above the melting point. The application of an annular ring can also be carried out by injection molding or by ultrasonic welding. The tubes 34 and 36 each have a type B jacket 0.345 mm thick, which is not modified by the hot-forming of the head, and their annular shoulder 38 has a thickness adjusted as required between 0.3 and 0.4 mm. In the case of tube 36 (Figure 9), the annular ring 37 occupies less than half the width of the annular shoulder 38; This can still be compressed well enough on the sides to improve the expulsion of the product.

The section through the tube 36, showing the connection of its shoulder 38 to the annular crown 37 (Figure 10), demonstrates the effectiveness of the compression and welding of the folds in the tapered head as well as the perfect welding of the annular crown 37:

- a double fold 39 of the barrier layer 20 has an end that has escaped the overlap and compression of the folds, with two subsequent, very thinned folds 41;

- a second portion 42 of the barrier layer 20 belongs to a fold which is welded to the double fold containing the double fold 39 of the barrier layer 20;

- at the right front end 40 and the double fold 39 is the ring 37, which, like the surface layers of the tube 36, is made of PE ;

- the welding of the folds between each other and between the folds forming the shoulder and the annular collar is perfectly continuous. The section shows the adhesive layers in places, such as 21, but there is no other interruption in the PE surrounding the elements described;

- the dilution obtained is amazing, it can be adjusted as required by selecting the hot molding temperature and the tool setting.

Commercial use

Tubes with an elastic plastic cover that improves the shelf life of the aroma or fragrance of the product they contain, such as a liquid, cream or paste. Tubes that also allow the product they contain to be dispensed more easily and completely. Particularly for the cosmetics, pharmaceuticals, hygiene, food and care products industries. Table 1 Weight gain of coat samples after four weeks of impregnation with a flavoured toothpaste Table 2 Maximum counterforce of the tube shells against indentation during the pressing test (Figure 4)

Claims (14)

1. Tube (B, C, 34, 36) for storing and dispensing a water-containing product, for example flavored or perfumed, with a dispensing head (38 and 35) attached to a flexible multilayer casing, the casing necessarily comprising an intermediate polymer layer with a barrier effect (20) for oxygen and aromas or fragrances, which is sensitive to moisture, and on each side of this intermediate layer one or more polymer layers (1, 100, 13, 11; and 12, 14, 10) based on polyolefin, all these layers being continuously connected to one another, characterized in that the total of the layers (1, 21; 100, 13, 11, 21) located on the inside of the intermediate layer with a barrier effect has a total thickness of between 55 and 140 µm, so that the aroma or the scent of a product that is contained therein or may be contained therein later is better preserved. 2. Tube according to claim 1, wherein the total thickness of the layers (1, 21; 100, 13, 11, 21) located on the inside of the intermediate layer is between 65 and 130 µm. 3. Tube according to one of claims 1 or 2, in which the polyolefin-based polymer layers consist partly of an inner surface layer of low or very low density polyethylene (1) or of linear low density polyethylene (100) with a specific weight of between 0.86 and 0.93 g/cm³ and partly of other layers each consisting of low density polyethylene (PE-LD) with a specific weight of between 0.90 and 0.93 g/cm³ or of high density polyethylene (PE-HD) with a specific weight of between 0.935 and 0.97 g/cm³ (13, 14). 4. Tube (B, 34, 36) according to claim 3, wherein the polyethylene layers contain one or more layers of PE-HD (13, 14) with a total thickness of at least 90 µm. 5. Tube according to claim 4, wherein the sum of the thicknesses of the PE-HD layers (13, 14) is between 100 and 140 µm and the thickness of the jacket is between 260 and 380 µm. 6. Tube according to claim 4, wherein the sum of the doubled thickness of the barrier layer (20) and the thicknesses of the PE-HD layers (13, 14) is between 130 and 180 µm and the thickness of the jacket is between 260 and 380 µm. 7. Tube according to one of claims 3 to 6, in which the polyethylene layers comprise a first PE-HD layer (13) which is inserted between the inner surface layer (100) and a first intermediate layer (11) made of PE-LD, which in turn lies within the intermediate layer with barrier effect (20). 8. Tube according to one of claims 3 to 7, in which the polyethylene layers comprise a second PE-HD layer (14) which is inserted between an outer PE-LD layer (10) and a second intermediate layer (12) made of PE-LD, which in turn lies outside the intermediate layer with barrier effect (20). 9. Tube according to one of claims 7 or 8, in which the first PE-HD layer (13) and/or the second PE-HD layer (14) is/are melt-continuously bonded to the PE-LD layers (100, 11; 12, 10) between which it is/are inserted. 10. Tube (B, 34, 36) according to claim 8, dependent on claim 7, wherein the thicknesses of the first and second PE-HD layers (13, 14) are between 10 and 50 µm and between 60 and 140 µm, respectively. 11. Tube (B, 34, 36) according to claim 10, wherein the first and second PE-LD intermediate layers (13, 14) are each connected to one side of the intermediate barrier layer (20) by a connecting layer (21, 22) made of EMA or EAA. 12. Tube according to one of claims 1 to 11, in which the intermediate layer with barrier effect (20) of the casing consists of a material from the group of EVAs, PVAs, PAs and modified PAs and has a thickness between 0.01 and 0.05 mm. 13. Tube (34, 36) according to one of the preceding claims, in which the dispensing head (38 and 35) comprises a neck (35) of smaller diameter than the jacket and an annular shoulder (38) connecting the neck (35) to the jacket (38), the shoulder having a thickness of between 0.9 and 1.35 times the thickness of the jacket, being in structural continuity with the jacket and having flattened folds welded together, this shoulder (38) being laterally compressible. 14. Tube (36) according to claim 13, wherein the flattened, welded folds contain folded and flattened extensions (39, 41) of the intermediate barrier layer (20) of the jacket.